Multi-powerhead outboard motor

ABSTRACT

Disclosed herein is an outboard motor comprising a lower unit rigidly connected to the bottom of a drive shaft housing and including a rotatably mounted propeller shaft supporting a propeller, first and second engines respectively including first and second crankshafts and respectively mounted to the top of the drive shaft housing with the first and second crankshafts extending at an acute angle to each other, first and second drive shafts respectively drivingly connected to the first and second crankshafts and respectively extending in the drive shaft housing and in the lower unit in co-axial relation to the first and second crankshafts, and gearing in the lower unit drivingly connecting the first and second drive shafts to the propeller shaft.

United States Patent Strang .Jan. 29, 1974 MULTl-POWERHEAD OUTBOARDMOTOR Primary Examiner-Duane A. Reger Assistant ExaminerJesus D. Sotelo[75] Inventor. Charles D. Strang, Lake Forest, Ill. Attorney g or FirmRobert E. Clemency et al- [73] Assignee: Outboard Marine Corporation,

Waukegan, Ill. [57] ABSTRACT [22] Fil d; Feb. 8, 1973 Disclosed hereinis an outboard motor comprising a lower unit'rigidly connected to thebottom of a drive [21] Appl' 330597 shaft housing and including arotatably mounted propeller shaft supporting a propeller, first andsecond 52 US. Cl. 115/17, 60/97 R engines respectively including firstand Second crank- 51 1111. C1 B63h 21/26 Shafts and respectively mountedto the p of the drive 58] Fi ld f S 1 1 15/12 A17 1 R, 1 A 34 R, shafthousing with the first and second crankshafts ex- 1 15/35; 123/195 P, 51BA; 74/661; 60/97 R tending at an acute angle to each other, first andsecond drive shafts respectively drivingly connected to [56] ReferencesCi d the first and second crankshafts and respectively ex- UNITED STATESPATENTS tending in the drive shaft housing and in the lower unit 708 4165/1955 Schmmer 74/66 in co-axlal relation to the first andsecondcrankshafts, 3025823 3/1962 Tenney 5/17 and gearing 1n the lower unitdrivingly connecting the 3:148:55? 9/1964 shimanc i;I::IIIIIIIIIIIII:115/18 first and Second Shafts the Propeller Shaft- 18 Claims, 6 DrawingFigures PATENTEI) JAN 2 91974 SHEET 2 [IF 2 MULTI-POWERHEAD OUTBOARDMOTOR BACKGROUND OF THE INVENTION The invention relates generally tooutboard motors and more particularly to outboard motors including twoengines. Examples of prior patents disclosing outboard motors with twoengines include the US. Moran Pat. No. 2,737,143 issued Mar. 6, 1956 andthe US Tenney Pat. No. 3,025,823 issued Mar. 20, 1962.

Examples of prior patents disclosing outboard motors with a singleoppositely acting engine including two spaced crankshafts include theUS. Bizet Pat. No. 1,707,897 issued Apr. 2, 1929, the US. Stucke Pat.No. 2,781,749 issued Feb. 19, 1957 and the US. Schimanckas Pat. No.3,148,557 issued Sept. 15, 1964.

The foregoing patents employ either two drive shaft housings andconnected lower units as in the Moran and Bizet patents or a singledrive shaft housing and lower unit powered by an oppositely actingengine as in the Stucke, Schimanckas and Tenney patents.

In both of the Stucke and Tenney patents, the crankshafts are drivinglyconnected adjacent to the engine block. In Schimanckas, parallel driveshafts extend from parallel crankshafts.

Attention is also directed to the US I-Iult Pat. No. 1,165,803 issuedDec. 18, 1915.

All of the above constructions suffer various relative disadvantages.For instance, the use of two drive shaft housings and lower units isrelatively expensive. In addition, the use of two lower units increasesthe drag or resistance to travel through the water. Use of gearing orother connections adjacent the engine block, as for instance in theTenney patent and in the Stucke patent, serves to increase weight andexpense and involves power loss. Lubrication of such gearing is afurther consideration involving added cost, weight and complexity.Furthermore, gear-boxes, such as are employed in the Tenney patent,interfere with exhaust gas flow to the drive shaft housing and withexhaust gas.

Use of a double acting engine, as disclosed particularly in FIG. 1 ofthe Schimanckas patent, serves to substantially increase the fore andaft distance between the parallel drive shafts and thereby to increasethe lower unit wetted area with consequent increased frictionalresistance to travel through the water. All of the above factors havepreviously indicated that more powerful outboard motors could be mosteconomically obtained by employing a single engine of larger horsepower.

SUMMARY OF THE INVENTION The invention provides an outboard motorincluding a single drive shaft housing and connected lower unit,together with two separate engines mounted to the top of the drive shafthousing with respective crankshafts extending at an acute angle to eachother and connected to the upper end of respective co-axially extendingdrive shafts which extend through the drive shaft housing and into thelower unit and which, at their lower ends, are connected by gearing to asingle propeller shaft rotatably supported in the lower unit.

In one embodiment, the engines are laterally spaced from each other andinclude respective pluralities of cylinders having axes extending inparallel relation to the propeller shaft. The engines are oppositelyfacing, i.e., the cylinders of one engine extend forwardly from theassociated crankshaft and the cylinders of the other engine extendrearwardly from the associated crankshaft. In addition, the crankshaftsand respectively connected drive shafts extend in an acute angle to eachother when viewed from a vertical plane perpendicular to the propellershaft and in parallel relation to each other when viewed from a verticalplane parallel to the propeller shaft.

In another embodiment, the engines are spaced in the fore and aftdirection, i.e., axially of the propeller shaft, and include respectivepluralities of cylinders having axes extending in parallel relation toone another and in lateral relation to the propeller shaft. The enginesare oppositely facing, i.e., the cylinders of one engine extendlaterally from the associated crankshaft in one direction and thecylinders of the other engine extend laterally of the associatedcrankshaft in the opposite direction. In addition, the crankshafts andthe respectively connected drive shafts extend in a plane common to thepropeller shaft and at an acute angle to each other when viewed from avertical plane in parallel relation to the propeller shaft.

One of the principal objects of the invention is the provision of amulti-engine outboard motor having a single lower unit with a minimumfrontal area.

Another of the principal objects of the invention is the provision of anoutboard motor including a single drive shaft housing and a pair ofinternal combustion engines mounted to the top of the drive shafthousing in such manner as to facilitate exhaust gas tuning andconventional discharge of exhaust gases through the drive shaft housing.

Another of the principal objects of the invention is the provision of ahigh horsepower outboard motor which is light in weight per unit ofhorsepower, which is simple in design, economical to construct, andwhich delivers maximum effective horsepower.

Other objects and advantages of the invention will become known byreference to the following description, claims and accompanyingdrawings.

THE DRAWINGS FIG. 1 is a side elevational view, partially in section, ofone embodiment of an outboard motor incorporating various of thefeatures of the invention.

FIG. 2 is a transverse view, partially in section, of the outboard motorshown in FIG. 1.

FIG. 3 is a schematic view of an alternate arrangement for connectingthe drive shafts and propeller shaft shown in FIGS. 1 and 2.

FIG. 4 is a side elevational view, partially in section, of a secondembodiment of an outboard motor incorporating various of the features ofthe invention.

FIG. 5 is a transverse view, partially in section, of the outboard motorshown in FIG. 4.

FIG. 6 is a schematic view of an alternate construction for connectingthe drive shafts and the propeller shaft shown in FIGS. 4 and 5.

Before explaining the invention in detail, it is to be understood thatthe invention is not limited in its application to the details ofconstruction and arrangement of parts set forth in the following generaldescription or illustrated in the accompanying drawings, since theinvention is capable of other embodiments and of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology or terminology employed herein is for the purpose ofdescription and not of limitation.

GENERAL DESCRIPTION Shown in FIGS. 1 and 2 is an outboard motor 11including a propulsion unit 13 comprising a single, hollow drive shafthousing 15 and a lower unit 17 rigidly connected to the lower end of thedrive shaft housing 15 and rotatably supporting a propeller shaft 19carrying a propeller 21. Also included in the propulsion unit 13 are twogenerally identically constructed, internal combustion engines 23 and25, which are respectively rigidly secured to the top of the drive shafthousing 15.

As is conventional practice, there is connected to the propulsion unit13 means adapted to be attached to a boat transom and affording bothvertical and horizontal swinging movement of the propulsion unit 13relative to the boat transom. While various other arrangements can beemployed, in the illustrated construction, such means comprises atransom bracket 31 adapted to be attached to the boat transom, and aswivel bracket 33 which is pivotally connected to the transom bracket 31about a horizontal tilt axis 35 to afford vertical swinging movementtherebetween and which is pivotally connected to the propulsion unit 13about a steering axis 37 provided by a king pin 39.

Each of the engines 23 and is of generally conventional construction andcan be of various multi-cylinder designs In the illustrated constructioneach engine 23 and 25 includes three cylinders 41 each having associatedtherewith a spark plug 43 and an individual carburetor 45. In addition,the engines 23 and 25 include respective crankshafts 47 and 49operatively connected with pistons (not shown) respectively operable inthe cylinders 41. Respective fly wheels 51 are attached to the top ofthe respective crankshafts 47 and 49.

In particular in accordance with the invention, the engines 23 and 25are mounted with their crankshafts 47 and 49 in acute angular relationto each other and, in the embodiment shown in FIGS. 1 and 2, inlaterally spaced relation to each other and with one engine facingforwardly, i.e, with the cylinders 41 extending forwardly from thecrankshaft 47 and with the other engine 25 extending rearwardly, i.e.,with the cylinders 41 extending rearwardly from the crankshaft 49, andin parallel relation to the propeller shaft 19 and to the othercylinders 41. In order to facilitate engine mounting in the desiredarrangement, the upper end of the drive shaft housing 15 is designed toprovide two angularly oriented mounting surfaces 55 and 57 which extendat an obtuse angle to each other when viewed from in front, i.e., whenviewed from a vertical plane extending perpendicular to the propellershaft 19.

Also in accordance with the invention, first and second drive shafts 61and 63 are respectively suitably coupled in any conventional manner tothe first and second crankshafts 47 and 49 and extend co-axially withthe respective crankshafts 47 and 49 downwardly within the drive shafthousing 15 and into the lower unit 17 for driving connection throughsuitable gearing 65 with the propeller shaft 19. When viewed from theside, i.e., from a vertical plane extending parallel to the propellershaft 19, the drive shafts 61 and 63 extend vertically in generallyparallel relation to each other and in adjacently spaced relation in thefore and aft direction, and when viewed from the front, i.e., from avertical plane perpendicular to the propeller shaft 19, the drive shafts61 and 63 extend in acute angular relation to each other and convergeadjacent to the propeller shaft 19. Any suitable means can be employedto rotatably support the drive shafts 61 and 63 in the drive shafthousing 15 and in the lower unit 17.

As shown best in FIG. 2, the drive shaft housing 15 and lower unit 17are generally of upwardly open V shape and neck-down to a minimalfrontal area in the vicinity immediately above the gearcase portion 69of the lower unit. Only the lower, relatively narrow portion of the Vshape configuration is normally immersed in water during operation.Specifically, only that area of the lower unit 17 located below thecavitation plate 67 is normally located underwater during operation.

Various gearing arrangements can be used to connect the drive shafts 61and 63 to each other and to the propeller shaft 19. In FIG. 1, two rightangle bevel gears 71 and 73 spaced axially of the propeller shaft 19 arepinned at 75 to the propeller shaft 19 for common rotation therewith andare respectively in mesh with bevel gears 77 and 79 respectively carriedby the drive shafts 61 and 63. In the arrangement shown in FIG. 1, thedrive shafts 61 and 63 both rotate in the same rotative direction.

Shown in FIG. 3 is another gearing arrangement for drivingly connectingthe drive shafts 61 and 63 to the propeller shaft 19. In the FIG. 3arrangement, a compound gear 81 is mounted in the lower unit 17 incoaxial relation to the propeller shaft 19 and for relative rotationtherebetween. The compound gear 81 includes oppositely facing rightangle bevel gears 83 and 85 in respective engagement with the bevelgears 77 and 79 fixed to the respective drive shafts 61 and 63. Inaddition, a second right angle bevel gear'87 is also rotatably mountedby the lower unit in co-axial relation to the propeller shaft 19 and forrelative rotation therebetween. The second bevel gear '87 is located aftof the compound gear 81 and is in mesh with the bevel gear 77 on the aftdrive shaft 61.

Mounted on the propeller shaft 19 for movement axially thereof and forcommon rotation therewith is a dog clutch 89 which is selectivelyengageable with the bevel gears 83 and 87 so as to afford forward,neutral, and reverse drive connection of the drive shafts 61 and 63 tothe propeller shaft 19. Various arrangements can be employed to shiftthe clutch dog 89. Connection of both of the drive shafts 61 and 63 tothe compound gear 81 serves to interconnect the engines 23 and 25 one toanother and, as a result, the drive shafts 61 and 63 counter rotate withrespect to each other.

Shown in FIGS. 4 and 5 is another embodiment of an outboard motor 111embodying various of the features of the invention. As in the outboardmotor 1 1 shown in FIGS. 1 and 2, the outboard motor 111 includes apropulsion unit 1 13 which is connected to a swivel bracket 133 forhorizontal steering therebetween and, in turn, the swivel bracket 133 isconnected to a transom bracket 131 for vertical swinging movementrelative thereto.

Also as in the outboard motor 111, the propulsion unit 113 includes ahollow drive shaft housing 115 and a lower unit 1 17 which is rigidlyattached to the bottom of the drive shaft housing 1 15 and whichrotatably supports a propeller shaft 119 carrying a propeller 121. In

carburetors 145. Still further, the engines 123 and 125 respectivelyinclude crankshafts 147 and 149 which are operably connected throughpistons (not shown) in the cylinders 141.

As in the outboard motor 11, the engines 123 and 125 are spaced fromeach other and are rigidly mounted to the upper end of the drive shafthousing 115 so that the crankshafts 147 and 149 extend at an acute angleto each other. However, as distinguished from the construction of theoutboard motor 11, in the outboard motor 111, the engines 123 and 125are located in fore and aft spaced relation to each other, i.e., arespaced axially of the propeller shaft 119, with the forward engine 123facing to one side, i.e., with the cylinders 141 extending laterallyfrom the crankshaft 147 to the left as shown in FIG. 5, and with thecylinders 141 of the aft engine 125 extending laterally from thecrankcase 149 to the other side, i.e., to the right in FIG. 5. Thus, inthe embodiment shown in FIGS. 4 and 5, the cylinder axes extendlaterally whereas in the embodiment shown in FIGS. 1 and 2 the cylindersaxes extend fore and aft.

In order to mount the engines 123 and 125 as above described, the driveshaft housing 115 includes, at the upper end thereof, two fore and aftangularly related mounting areas 155 and 157 to which the engines 123and 125 are respectively rigidly connected.

Extending through the drive shaft housing 115 and into the lower unit119 are fore and aft drive shafts 161 and 163 which extend co-axiallyfrom and are suitably drivingly coupled to the fore and aft crankshafts147 and 149. At their lower ends, the drive shafts 161 and 163 aredrivingly connected to the propeller shaft 119 by suitable gearing 165.While other arrangements are possible, in the construction illustratedin FIG. 4 and 5, the propeller shaft 119 has pinned thereto a compoundgear 181 having fore and aft facing bevel gears 183 and 185 which arerespectively meshed with bevel gears 177 and 179 on the respective driveshafts 161 and 163.

As can be seen from FIGS. 4 and 5, the drive shafts 161 and 163 extendin co-planar relation with each other and with the propeller shaft 119and in fore and aft spaced relation. When seen from the side, i.e., froma vertical plane parallel to the propeller shaft 119, the drive shafts161 and 163 extend in acute relation to each other and converge in thedownward direction. Various suitable bearing means can be employed torotatably support the drive shafts 161 and 163 in the drive shafthousing 115 and in the lower unit 117.

As can be seen especially in FIG. 5, the lower unit has a relativelynarrow frontal area between the cavitation plate 167 and the gear case169.

Shown in FIG. 6 is another gearing arrangement including a reversingtransmission. The gearing arrangement is similar to that disclosed inFIGS. 4 and 5 except that the compound gear 181 is not pinned to thedrive shaft 119 and is rotatable relative thereto and supported from thelower unit 117 in co-axial relation to the propeller shaft 119. Alsoincluded in the gearing arrangement shown in FIG. 6 is a second bevelgear 187 which is mounted in spaced relation aft of the compound gear181 and in co-axial relation to the propeller shaft 119 for relativerotation therebetween. The second bevel gear 187 is smaller than therearwardly facing gear 185 on the compound gear 181 and is also in meshwith the bevel gear 179 on the after drive shaft 163.

Located between the bevel gears 183 and 187 is a clutch dog 189 which isslidable axially on the propeller shaft 119 and which rotates in commonwith the propeller shaft 119 and which is selectively engageably withthe bevel gears 185 and 187 to provide forward, neutral, and reversedrive conditions. Various arrangements can be employed to shift the dogclutch between its various positions.

In the gearing arrangement disclosed in FIGS. 4 through 6, the driveshafts 161 and 163 counter rotate. If desired, an arrangement similar tothat shown in F IG. 1 could be employed if it is desired to have thedrive shafts 161 and 163 rotate in the same direction.

Both of the disclosed embodiments incorporate two separate and generallyidentical engines which are separately and rigidly mounted in spaced andangular relation to each other on the top of a drive shaft housing. Sucharrangement allows exhaust gas discharge through the drive shaft housingusing conventional techniques and without interference from gearinglocated above or within the drive shaft housing. In particular, tuningtubes can be employed so as to improve engine performance and exhaustgas discharge can be either through a snout 200 as shown in FIGS. 1 and4 or through a propeller hub as is also conventional.

It is noted that one-half of the total horsepower of the outboard motor,i.e., the output of each engine, is directly transmitted from theapplicable engine to the propeller shaft through independent driveshafts and through bevel gearing which is smaller than if the entirehorsepower output of the outboard motor were transmitted through asingle set of bevel gears. Thus, notwithstanding large horsepowerdelivery, the frontal area of the lower unit can be relatively small soas to avoid power losses due to water resistance.

Because the engines of the embodiment of FIGS. 1 and 2 are reverselyoriented, and because the engines in the embodiment of FIGS. 4 and 5 aresupported in angular relation to each other (as seen best in FIG. 4) thedrive shafts can enter the lower unit in relatively adjacent relation toeach other in the fore and aft direction, and thereby avoid excessivelength in the fore and aft dimension of the lower unit.

Connection of the drive shafts to each other in the lower unit eitherthrough a compound gear (see FIGS. 3, 4 and 6) or through a propellershaft (see FIG. 1) serves to avoid problems associated with equalizingpower delivery through a double drive shaft arrangement powered by asingle engine.

In general, the disclosed constructions provide an outboard motor orrelatively high horsepower output with a relatively small lower unitfrontal area and with minimum weight, economic cost, and power loss, andwith freedom from various of the complexities found in the prior art.

In addition, the employment of relatively long drive shafts which have alow torsional frequency, serves to reduce or substantially eliminate thepossibility of developing critical vibrations in the drive train of theoutboard motor.

Various of the features of the invention are set forth in the followingclaims.

I claim:

1. An outboard motor comprising a propulsion unit including a driveshaft housing, a lower unit rigidly connected to the bottom of saiddrive shaft housing and including a rotatably mounted propeller shaftsupporting a propeller, first and second engines respectively includingfirst and second crankshafts and being respectively mounted to the topof said drive shaft housing with said first and second crankshaftsextending at an acute angle to each other, first and second drive shaftsrespectively drivingly connected to said first and second crankshaftsand respectively extending in said drive shaft housing and in said lowerunit in co-axial relation to said first and second crankshafts, andgearing in said lower unit drivingly connecting said first and seconddrive shafts to said propeller shaft and means adapted to be connectedto a boat hull and connected to said propulsion unit to afford verticaland horizontal swinging movement of said propulsion unit relative to theboat hull.

2. An outboard motor in accordance with claim 1 wherein said first andsecond engines respectively inelude a plurality of cylinders extendingin parallel relation to one another.

3. An outboard motor in accordance with claim 2 wherein all of saidcylinders have axes extending parallel to said propeller shaft and saidcylinders of said first engine extend forwardly of said first crankshaftand wherein said cylinders of said second engine extend rearwardly ofsaid second crankshaft.

4. An outboard motor in accordance with claim 2 wherein said first andsecond engines are laterally spaced from each other.

5. An outboard motor in accordance with claim 2 wherein all of saidcylinders have axis extending laterally to said propeller shaft and saidcylinders of said first engine extend laterally from said firstcrankshaft in one direction and said cylinders of said second engineextend laterally from said second crankshaft in the direction oppositefrom said one direction.

6. An outboard motor in accordance with claim 2 wherein said first andsecond engines are spaced from each other in the direction of the axisof said propeller shaft.

7. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts extend at an acute angle to each other when viewed ina vertical plane perpendicular to said propeller shaft.

8. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts extend in parallel relation to each other when viewedin a vertical plane parallel to said propeller shaft.

9. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts extend at an acute angle to each other when viewed ina vertical plane extending parallel to said propeller shaft.

10. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts extend in a common vertical plane containing saidpropeller shaft.

11. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts counter rotate.

12. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts rotate in the same rotative direction.

13. An outboard motor propulsion unit including a drive shaft housing, alower unit rigidly connected to the bottom of said drive shaft housingand including a rotatably mounted propeller shaft supporting apropeller, first and second engines mounted to the top of said driveshaft housing in laterally spaced relation to each other andrespectively including respective first and second crankshafts, andrespective pluralities of cylinders extending in parallel relation toone another in parallel relation to said propeller shaft with saidcylinders of said first engine extending forwardly of said firstcrankshaft and said cylinders of said second engine extending rearwardlyof said second crankshaft, first and second drive shafts respectivelydrivingly connected to said first and second crankshafts andrespectively extending in said drive shaft housing and in said lowerunit in co-axial relation to said first and second crankshafts, saidfirst and second drive shafts extending at an acute angle to each otherwhen viewed in a vertical plane perpendicular to said propeller shaftand extending in parallel relation to each other when viewed in avertical plane parallel to said propeller shaft, and gearing in saidlower unit drivingly connecting said first and second drive shafts tosaid propeller shaft.

14. An outboard motor propulsion unit in accordance with claim 13wherein said first and second crankshafts counter rotate.

15. An outboard motor propulsion unit in accordance with claim 13wherein said first and second crankshafts rotate in the same rotativedirection.

16. An outboard motor propulsion unit including a drive shaft housing, alower unit rigidly connected to the bottom of said drive shaft housingand including a rotatably mounted propeller shaft supporting apropeller, first and second engines respectively rigidly mounted to thetop of said drive shaft housing in spaced relation to each other axiallyof said propeller shaft and including respective first and secondcrankshafts extending at an acute angle' to each other, and respectivepluralities of cylinders extending in parallel relation to one anotherwith said cylinders of said first engine extending laterally from saidfirst crankshaft in one direction and said cylinders of said secondengine extending laterally from said second crankshaft in the directionopposite from said one direction, first and second drive shaftsrespectively drivingly connected to said first and second crankshaftsand respectively extending in said drive shaft housing and in said lowerunit in co-axial relation to said first and second crankshafts, saidfirst and second drive shafts extending in a common vertical planecontaining said propeller shaft and at an acute angle to each other whenviewed in a vertical plane extending parallel to said propeller shaft,and gearing in said lower unit drivingly connecting said first andsecond drive shafts to said propeller shaft.

17. An outboard motor propulsion unit in accordance with claim 16wherein said first and second crankshafts counter rotate.

18. An outboard motor propulsion unit in accordance with claim 16wherein said first and second crankshafts rotate in the same rotativedirection.

1. An outboard motor comprising a propulsion unit including a driveshaft housing, a lower unit rigidly connected to the bottom of saiddrive shaft housing and including a rotatably mounted propeller shaftsupporting a propeller, first and second engines respectively includingfirst and second crankshafts and being respectively mounted to the topof said drive shaft housing with said first and second crankshaftsextending at an acute angle to each other, first and second drive shaftsrespectively drivingly connected to said first and second crankshaftsand respectively extending in said drive shaft housing and in said lowerunit in co-axial relation to said first and second crankshafts, andgearing in said lower unit drivingly connecting said first and seconddrive shafts to said propeller shaft and means adapted to be connectedto a boat hull and connected to said propulsion unit to afford verticaland horizontal swinging movement of said propulsion unit relative to theboat hull.
 2. An outboard motor in accordance with claim 1 wherein saidfirst and second engines respectively include a plurality of cylindersextending in parallel relation to one another.
 3. An outboard motor inaccordance with claim 2 wherein all of said cylinders have axesextending parallel to said propeller shaft and said cylinders of saidfirst engine extend forwardly of said first crankshaft and wherein saidcylinders of said second engine extend rearwardly of said secondcrankshaft.
 4. An outboard motor in accordance with claim 2 wherein saidfirst and second engines are laterally spaced from each other.
 5. Anoutboard motor in accordance with claim 2 wherein all of said cylindershave axis extending laterally to said propeller shaft and said cylindersof said first engine extend laterally from said first crankshaft in onedirection and said cylinders of said second engine extend laterally fromsaid second crankshaft in the direction opposite from said onedirection.
 6. An outboard motor in accordance with claim 2 wherein saidfirst and second engines are spaced from each other in the direction ofthe axis of said propeller shaft.
 7. An outboard motor in accordancewith claim 1 wherein said first and second crankshafts extend at anacute angle to each other when viewed in a vertical plane perpendicularto said propeller shaft.
 8. An outboard motor in accordance with claim 1wherein said first and second crankshafts extend in parallel relation toeach other when viewed in a vertical plane parallel to said propellershaft.
 9. An outboard motor in accordance with claim 1 wherein saidfirst and second crankshafts extend at an acute angle to each other whenviewed in a vertical plane extending parallel to said propeller shaft.10. An outboard motor in accordance with claim 1 wherein said first andsecond crankshafts extend in a common vertical plane containing saidpropeller shaft.
 11. An outboard motor in accordance with claim 1wherein said first and second crankshafts counter rotate.
 12. Anoutboard motor in accordance with claim 1 wherein said first and secondcrankshafts rotate in the same rotative direction.
 13. An outboard motorpropulsion unit including a drive shaft housing, a lower unit rigidlyconnected to the bottom of said drive shaft housing and including arotatably mounted propeller shaft supporting a propeller, first andsecond engines mounted to the top of said drive shaft housing inlaterally spaced relation to each other and respectively includingrespective first and second crankshafts, and respective pluralities ofcylinders extending in parallel relation to one another in parallelrelation to said propeller shaft with said cylinders of said firstengine extending forwardly of said first crankshaft and said cylindersof said second engine extending rearwardly of said second crankshaft,first and second drive shafts respectively drivingly connected to saidfirst and second crankshafts and respectively extending in said driveshaft housing and in said lower unit in co-axial relation to said firstand second crankshafts, said first and second drive shafts extending atan acute angle to each other when viewed in a vertical planeperpendicular to said propeller shaft and extending in parallel relationto each other when viewed in a vertical plane parallel to said propellershaft, and gearing in said lower unit drivingly connecting said firstand second drive shafts to said propeller shaft.
 14. An outboard motorpropulsion unit in accordance with claim 13 wherein said first andsecond crankshafts counter rotate.
 15. An outboard motor propulsion unitin accordance with claim 13 wherein said first and second crankshaftsrotate in the same rotative direction.
 16. An outboard motor propulsionunit including a drive shaft housing, a lower unit rigidly connected tothe bottom of said drive shaft housing and including a rotatably mountedpropeller shaft supporting a propeller, first and second enginesrespectively rigidly mounted to the top of said drive shaft housing inspaced relation to each other axially of said propeller shaft andincluding respective first and second crankshafts extending at an acuteangle to each other, and respective pluralities of cylinders extendingin parallel relation to one another with said cylinders of said firstengine extending laterally from said first crankshaft in one directionand said cylinders of said second engine extending laterally from saidsecond crankshaft in the direction opposite from said one direction,first and second drive shafts respectively drivingly connected to saidfirst and second crankshafts and respectively extending in said driveshaft housing and in said lower unit in co-axial relation to said firstand second crankshafts, said first and second drive shafts extending ina common vertical plane containing said propeller shaft and at an acuteangle to each other when viewed in a vertical plane extending parallelto said propeller shaft, and gearing in said lower unit drivinglyconnecting said first and second drive shafts to said propeller shaft.17. An outboard motor propulsion unit in accordance with claim 16wherein said first and second crankshafts counter rotate.
 18. Anoutboard motor propulsion unit in accordance with claim 16 wherein saidfirst and second crankshafts rotate in the same rotative direction.